Some missing persons cases have been waiting for testing at the FBI for nine years according to the report.

The report notes an example of a mother who was waiting to see if the bodies of two unidentified children were indeed her children. Because of the backlog there was a three-month delay. The report indicates the mother "called the [law enforcement agency] daily for notification on the progress of the testing."

The lab has an overall backlog of 3,211 cases - which would take two years to clear, even without the addition of new cases - but the authors note that because missing persons cases often lack the urgency of a trial date and a suspect, they are not prioritized.

Other backlogged cases included criminal cases from Indian Country, intelligence and improvised explosive device testing from war zones.

The report also notes that while the Washington, DC Police Department has depended on the FBI lab for forensic analysis, the police department has lost evidence in at least 160 cases.

"We are very concerned about a comment made in the report attributed to unnamed FBI "lab personnel" that "MPD cannot locate evidence for over 200 cases". We intend to make a formal inquiry of the FBI OIG to see if we can get additional information regarding this allegation," said Gwendolyn Crump, Spokesperson, Metropolitan DC Police Department.

The Inspector General also criticizes the FBI for the slow and costly implementation of a new data tracking system that so far has cost over $8.9 million and taken five years.

The FBI concurred with all of the Inspector General's recommendations for improvement including standardizing backlog definitions, updating the computer system and evaluating the outsourcing agreements the FBI has with private labs to reduce the backlog.